Mobile phones, personal digital assistants (“PDAs”), digital cameras, MP3 players, and other portable electronic devices utilize SSL devices (e.g., LEDs) for background illumination. SSL devices are also used for signage, indoor lighting, outdoor lighting, and other types of general illumination. FIG. 1A is a cross-sectional view of a conventional SSL device 10a with lateral contacts. As shown in FIG. 1A, the SSL device 10a includes a substrate 20 carrying an LED structure 11 having an active region 14, e.g., containing gallium nitride/indium gallium nitride (GaN/InGaN) multiple quantum wells (“MQWs”), positioned between N-type GaN 15, and P-type GaN 16. The SSL device 10a also includes a first contact 17 on the P-type GaN 16 and a second contact 19 on the N-type GaN 15. The first contact 17 typically includes a transparent and conductive material (e.g., indium tin oxide (“ITO”)) to allow light to escape from the LED structure 11. FIG. 1B is a cross-sectional view of another conventional LED device 10b in which the first and second contacts 17 and 19 are opposite of each other, e.g., in a vertical rather than lateral configuration. In the LED device 10b, the first contact 17 typically includes a reflective and conductive material (e.g., aluminum) to direct light toward the N-type GaN 15.
As discussed in more detail below, the various elements of the SSL devices typically have different coefficients of thermal expansion (CTE). During temperature excursions that occur in manufacturing processes and/or during use, the difference in CTEs of the device elements may cause the elements to delaminate. In addition, as is also discussed in more detail below, several elements of the SSL device are grown epitaxially on the substrate 20. It is accordingly desirable to control the growth of the materials forming these elements in a manner that improves the performance and reliability of the resulting device.